1. Technical Field
The present disclosure relates to a technique for use in lensless microscopes to generate an image of an object by using a virtual focal plane on the basis of a plurality of images captured by using a plurality of light sources.
2. Description of the Related Art
There is a need for continuous observation of cultured cells without staining the cells in many fields in which cultured cells are used for medical and industrial purposes, such as production of cells for use in medical treatment and investigation of the efficacy of a medicine. However, since most cells are colorless and transparent, the three-dimensional structure of cultured cells is not clearly revealed by imaging with optical microscopes using transmitted light.
Japanese Unexamined Patent Application Publication No. 2013-101512 discloses a method for generating an in-focus image (virtual sectional image) at a plane that is not parallel to an objective lens from many images for which the focal plane is parallel to the objective lens and the focal point is at different heights with respect to an object (i.e., many images captured by changing the focus along a height direction of the object) in order to evaluate the sectional profile of cells.
Continuous observation of cultured cells is carried out in a limited space, such as an incubator, in order to maintain a humid environment for culturing the cells. To enable observation in a limited humid space, U.S. Patent Application Publication No. 2014/0133702 discloses a lensless microscope that enables observation of minute cells without using lenses. U.S. Patent Application Publication No. 2014/0133702 discloses a method for increasing the resolution by superimposing a plurality of images captured under illumination from a plurality of different positions (ptychography).
According to the method disclosed in Japanese Unexamined Patent Application Publication No. 2013-101512, since a partial image is extracted from each image at a corresponding one of the heights after imaging and then the extracted partial images are linked together, the joints of the partial images become discontinuous. Consequently, the image quality of the virtual sectional image degrades due to discontinuity. In addition, if processing for blurring is performed on the discontinuous portions to decrease the degradation of image quality due to discontinuity, the sharpness of the virtual sectional image decreases.